McConnell and his team used ice cores — long cylinders of ice removed by a powerful drill — to provide a vertical timeline of past climates stored in the ice sheets of Greenland. Ice cores can provide an annual record of temperature, precipitation, atmospheric composition, volcanic activity and wind patterns, according to NASA.

Thousands of years ago, when the ancient Greek and Roman empires ruled over Europe, lead was mined and smelted to produce water pipes and ship sheathing, for example.

The lead pollution drifted some 2,800 miles north with the winds over the ocean to Greenland and settled into the ice. Then, each year, as snowfall added layers to the ice sheet, lead emissions were captured along with dust and other airborne particles, and became part of the ice-core record that scientists use today to learn about conditions of the past.

Lead pollution emissions began to rise as early as 900 B.C., the study said, as Phoenicians expanded their trading routes into the western Mediterranean.

During prosperous times, lead pollution was more plentiful, indicating a strong economy. According to the study, the highest levels of lead pollution emissions coincided with the height of the Roman Empire during the 1st and 2nd centuries, a period of economic prosperity known as the Pax Romana.

Plagues, wars and political instability decreased the amount of lead found in the Greenland ice over the next few centuries.

"The great Antonine Plague struck the Roman Empire in A.D. 165 and lasted at least 15 years," said study co-author Andrew Wilson, an archaeologist from the University of Oxford. "The high lead emissions of the Pax Romana ended exactly at that time and didn't recover until the early Middle Ages, more than 500 years later," he said.

The study's research team included an unusual combination of scholars, including ice-core specialists, atmospheric scientists, archaeologists and economic historians.